In the Stofko U.S. Pat. Nos. 4,107,379 and 4,183,997 there are disclosed procedures for bonding lignocellulose materials including wood particles by the use of carbohydrates as adhesives. The sugars and starches used as the adhesives for the lignocellulosic materials are transformed by acidic and/or alkaline catalysts to water insoluble binders in situ by heat and pressure. It is believed that bonding is effected by chemical transformation of the carbohydrates to furans and the coupling of such furans with the lignin or other phenolic materials which are present on the surface of the lignocellulose. In view of the fact that it is known that in the presence of acids lignin becomes more reactive, it is theorized that the natural lignin present on the lignocellulose materials is activated by acidic catalyst.
It has also been previously known that furfural produced from pentose sugars or hydroxymethyl furfural produced from hexose sugars or starches react with phenols to produce phenol-furfural condensation resin. These resins have been produced commercially in the past.
In the consolidation of the lignocellulose materials, pressure has normally been applied by the use of massive presses with heat being provided by conduction through the press face to the lignocellulose materials under compaction. However, the use of steam in direct contact with the lignocellulosic material is not entirely unknown, and steaming apparatus for the consolidation of composite products are disclosed in Corbin U.S. Pat. Nos. 3,295,167; Shen 3,891,738; and Nyberg 4,162,877. Insofar as is known, in all the prior systems which have directly contacted the lignocellulosic material with steam, the conventional resins such as phenol-formaldehyde condensation product has always been used. These prior attempts have not solved the problem of providing superior particle board at the lowest possible price.